The operation of personal computers and other electronic devices is usually accompanied by high-frequency noise generated in the same device or transmitted from other apparatus. Among various methods proposed to solve this problem, that is, to eliminate high-frequency noise, the use of filters is one of the best known. Recent trends toward reducing the size and cost of electronic devices have had an influence on the filter design as well. An example of a filter design in accordance with such requirements is shown in FIG. 5, U.S. Pat. No. 4,791,391. This filter 100, as shown in FIG. 5, is built on alumina substrate 106 which has a through hole 104 through which passes contact 102 of an electrical connector; it is formed by the thick-film capacitor 116 consisting of lower electrode 110 connected to metal shell 108 of the electrical connector, dielectric layer 112, and upper electrode 114 soldered to contact 102. This filter can remove from the signal high-frequency noise passing along contact 102 by diverting it through the thick-film capacitor 116 to shell 108. Layers 110, 112, 114 which make up the capacitor 116 arm applied by screen printing technique. They can be made in sufficiently small sizes and at reasonably low cost.
However, since the dielectric layer 112 of filter 100 covers almost the entire surface of the alumina substrate 106 except for the through hole 104, the dielectric layer is shared by all contacts 102 passing through the alumina substrate 106. Therefore, portions of the dielectric layer common to the adjacent contacts 102 create a parasitic capacitance. This phenomenon becomes especially noticeable with the reduction of the connector size which results in an increased contact density. The increase in density of contacts 102, in turn, leads to a decrease in a capacitance of the thick-film capacitor, to an increase in the parasitic capacitance, and to signal leaks or crosstalk between adjacent contacts due to the increase in intercontact capacitance.
The purpose of this invention is to provide a filter and a connector with filter satisfying the small size and low cost requirements and, at the same time, eliminating crosstalk.